Method of and apparatus for simultaneous impact crushing of separate streams of sized rock



April 26, 1949.- J. BLAND METHOD OF AND APPARATUS FOR SIMULTANEOUSIMPACT CRUSHING OF SEPARATE STREAMS OF SIZED ROCK Filed March 15, 1945 On 0 n a 3Q a 00 a m 4 9. w. 0% O 5 n 4 L 00 000 0 40 o o c v 9 0 09 c 90 0 W0 0 00 o 00 0 o 00.0 0 6 900000 L w 0 nw WO O O QD Q %00 90%00000 05 wwa.z

- TOR. JOl/V 5444/0 ATTORNEXG Patented Apr. 26," 1949 METHOD OF ANDAPPARATUS FOR SIMUL- TANEOUS HWPKCT CRUSHING OF SEX- ABATE STREAMS FSIZED ROCK John Bland, Pacific Palisades, Calif.

Application March 1 5, 1945, Serial No. 582,924

2 Glaims. 1

This invention relates to a method and apparatus for crushing orpulverizing various materials, and has been primarily devised forcrushing or pulverizing hard or silicious rocks or ores although it maybe used for other analogous purposes.

One object of the invention is to provide a method for crushing orpulverizing hard rocks wherein astream of the rock to be crushed is fedinto the path of impact shoes of a rotary impeller or hammer whichstrike the rock at avery high speed and practically instantaneouslychange its direction ofv movement. The speeds of the impact shoesemployed may vary from 8000- linear feet per minute to 20,600 linearfeet per minute, or more, and by their sudden impact and change ofdirection of movement of the rock impacted the rock is crushed or brokenand in fact appears to virtually explode into small fragments. Thesefragments in turn may be thrown against an impact plate where at highspeeds additional breaking or pulverizing may occur. Impact crushers ofthis general type have heretofore been used on soft or sedimentary rockwherein the impact crusher may operate at a comparatively low speed.Usually however attempts at using an impact crusher on hard or siliciousrocks have been unsuccessful due to the failure or inability of theimpeller to stand up under the severe shocks occasioned by the requireduse of high speeds and the encountering of the harder rock. To overcomethis diificul-ty I employ an impeller that islargely a monolithicstructure except for replaceable impact shoes, such monolithic structureeither being formedby a single casting to which the shoes are attachedor if fabricated. its parts are welded together so as to thus berendered an integral construction.

Another object of the invention is to provide a method and apparatuswherein the rock is fed into the path of the shoes on the rotary hammeror impeller so as to reduce wear thereon. Heretofore, in impact crushersof this general character it has been common practice to drop all of therock to be crushed. in a common stream or chute with all sizes mixedtogether into the path of the shoes. This enablesthe larger pieces ofrock to fall into direct contact with the. shoesresulting in a veryrapid wearing. away of their faces due to chipping, flaking, or pittingof'the metal. The bringing of the larger pieces of rock:

into direct contact with the shoes also tends to. limit thespeed ofrevolution and the. force of:

the crushing blow because of the limited capacity of therevolvingstructure to absorb such heavy shocks. The wear to which the shoes aresubjected is essentially of two kinds, namely the rubbing. or scratchingaway of the metal due to rubbing of the rock relative to the shoesoccasioned by the rock tending to slide thereon when it encounters theshoes at an angle and the direct impact occasioned by large rocks beingsquarely struck by the shoes. The rubbing or scratching; of the metalcan to a large extent be reduced or eliminated. by directing the rockinto the path of the. moving impact shoe so that the departure from thenormal angle of incidence is as little'possible. The use of a very highspeed of" impact will normally accomplish this; High speed, however,will increase thewear due to impact which results in the pitting.chipping, flaking, or breaking way of small pieces of the faces of theshoes.

An object of the present invention is to provide an improved method andapparatus wherein the impeller may be driven at high speed to thusreducethe rubbing or simple attrition and which makes provision forreducing the effect of the impact occasioned by large rocks being struckdirectly by the face of the impact shoes.

Still a further object of the invention is to provide a method andapparatus f or crushing rock and like substances wherein there is acontinuously flowing circulatory path for the rock into whichisintroduced new'rock. to be crushed. and from which it is continuouslyextracted to crush rock. wherein the rock is segregated into large andsmall sizes which are fed into the path of the shoes in such: a mannerthat the smaller particles are interposed between the shoes and thelarge rocks thus protecting the. shoes from wear occasioned by heavyimpact. This arrangement of feeding the rock into the path of theimpeller enables the rock to be crushed very much finer than has beenheretofore accomplished by impact type crushers.

With the foregoing and other objects in. View, which will be mademanifest in the following detailed description and specifically pointed:out in. the appended claims, reference is had to the accompanyingdrawings for an illustrative embodiment of the invention, wherein:

The figure is a diagrammatic sectional view of an apparatus that may beemployed to carry out the present: invention.

Referring to' the accompanying drawingswherein. similar referencecharacters designate similar parts throughout,. Ht indicates an. endlessconveyor belt on which: new rock: to. be crushed indicated at I I may beconveyed to a sump or bin 12. A bucket elevator I3 or the equivalentserves to elevate this rock from the bin l2 and discharge it into anupper hopper 14 to be deposited on a vibrating screen 15. Beneath thisvibrating screen there is a second and finer vibrating screen l6 whichpermits fine particles ll to pass therethrough and to be deposited in ahopper it. These fine particles which pass through the lower vibratingscreen it may represent the finished product. The two screens may bevibrated in any suitable manner so as to cause the rock to passthereover and the finer particles to pass therethrough. Those particlesindicated at it which pass through the upper screen 15 and which arecaught on screen it are relatively small but are not small enough to beregarded as the finished product. The rock which passes over the upperscreen l ultimately passes onto a relatively coarse vibrating screen 20which permits relatively large rocks to pass therethrough and if desiredthere may be a vibrating screen 2| positioned therebelow which willcatch the largest rocks but permit rocks of intermediate size indicatedat 22 to pass therethrough. The smallest rocks which are caught onscreen it ultimately pass into a chute 23, the intermediate rocksthrough a chute 2d, and the large rocks into a chute 25. These chutesfeed these streams in consecutive order so that they will fall in frontof shoes 26 on the rotary impeller 21 mounted on a shaft 28 andpreferably rendered integral therewith. Shaft 28 may be driven at highspeed are fed into the path of the impact shoes 26 so that they are atfirst to be encountered by the shoes. The large rock particles which arefed through chute 25 are those which are most remote from the shoes. Theintermediate particles occupy position-s between the smallest particlesand the largest particles. By operating the impeller at high speedsliding of the rock relatively to the shoes is to a large extenteliminated so that wear of the shoes by simple attrition or sliding orscratching is largely eliminated. The impact wear is also minimized dueto the fact that the large rock particles do not come into directengagement with the faces of the shoes. The intermediate and smallerparticles prevent such direct engagement and as the smaller particleswhich drop directly against the faces of the shoes have little inertia,these particles do not tend to pit or break off or fiake off the shoefaces. The speed of rotation of the shoes is maintained quite highnormally ranging from 8000 linear feet per minute to 20,000 linear feetper minute. The falling rock which is encountered by the shoes has itsdirection changed almost instantaneously resulting in the large rockparticles being broken into small fragments. These rocks fairly seem toexplode under these conditions. The smaller rock particles are brokenfurther by being thrown against and grinding against the larger rockparticles as soon as suffering direct impacts from the shoes. The rockparticles after striking the impact plate 29 and being somewhat furtherbroken up descend and pass on the conveyor H] with the .4 incoming rockll into the sump. On being carried up by the elevator I3 those particleswhich are small enough to represent the finished product pass throughscreens l5 and [6 into the hopper I1. Those particles which are notquite small enough to represent the finished product are caught onscreen l6 and pass into chute 23 to represent the smaller particles thatserve to protect the faces of the shoes. The intermediate particlesdescend through chute 24 and the larger particles through chute 25.

It will, of course, be appreciated that the use of three chutes is notnecessary. The screening of the rock merely into two sizes is quitefeasible in which case, the smaller particles are fed into the path ofthe shoes 26 so that they will protect the faces of the shoes fromcoming into direct contact with the large rock sizes. It is likewisefeasible to increase the number of chutes in excess of three in whichcase the large rock sizes will be fed into the path of the shoe mostremote from the face thereof.

I find that with this construction a rotary impact crusher may besatisfactorily employed for crushing hard silicious rocks asdistinguished from soft or sedimentary rocks. By employing a monolithictype impeller it will stand up under high speed and under the severeimpacts occasioned thereby. The use of high speeds will alone minimizeattrition or abrasion of the rock on the faces of the shoes. However, byfeeding the rock in such a manner that the small particles areinterposed between the large rock and the faces of the shoes impact wearon the faces of the shoes will likewise be minimized. It is notnecessary to perform the improved method with the high speeds heretoforementioned, although these speeds are desirable in crushing many types ofhard rock. Where a coarser finished product is desired the impeller maybe driven at materially lower speeds than 8000 linear feet per minute,and when slower speeds are used I find that the interposing of thesmaller particles between the large rock and the shoe faces reducesabrasive wear on the shoes which would otherwise occur due to the slowerspeed employed.

It will be appreciated that the above-described method and apparatusthat rock may be continuously fed to the apparatus and the finishedproduct continuously withdrawn therefrom and that the same screeningoperation may be used to separate the finished product and to segregatethe rock that is fed to the impeller into large and. small sizes withthe small sizes being utilized to protect the shoe faces from the heavyimpacts of the large rocks.

The interposing of small rock between the large rock and the shoes alsoenables larger rock to be fed into the path of the impeller than wouldotherwise be possible. It also enables the finished product to becrushed to a much finer condition in that the fine particles whichdescend through chutes 23 are interposed between the impeller shoes andthe larger rock particles. These fine particles which have small massesand consequently small inertia which are not conducive to their beingbroken by impact alone are thus interposed or trapped between the shoesand the large rock particles which have greater inertia. Consequentlythe small rock particles are effectively pounded by the shoes againstthe large rock particles and are pulverized therebetween to a greaterextent than where the small rock particles are merely subjected toimpact alone. In this way a finished product may be obtained wherein therock is finely ground or pulverized which is highly desirable in certainoperations.

Various changes may be made in the details of construction withoutdeparting from the spirit and scope of the invention as defined by theappended claims.

I claim:

1. The method of crushing rock which includes providing a circulatorypath for rocks, introducing rock to be crushed into the path,segregating crushed rock from the path representing the finishedproduct, classifying the rock to be crushed according to size andfeeding the classified rocks in parallel paths into the path of a rotaryimpeller disposed in said circulatory path with the small rocks arrangedto engage the impeller first, and returning the crushed rock to saidpath.

2. An apparatus for crushing rock comprising means providing acirculatory path, means for introducing rock to be crushed into saidpath, screening means for screening out crushed rock representing thefinished product, screening means for segregating large rock from smallrock to be crushed, a rotary impeller disposed in said REFERENCES CITEDThe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,110,851 Symons Mar. 8, 19382,287,799 I-Iartshorn June 30, 1942' 2,292,852 Werner Aug. 11, 19422,316,124 Sheldon Apr. 6, 1943 OTHER REFERENCES New Holland DoubleCrusher Bullletin No. 651 of New Holland Machine Company, New Holland,Pennsylvania. Pub. Nov. 6, 1944. -8 Page C'OPY in Div. 25.

